ATKINSON— TWIN HYBRIDS. 133 



were strongly toothed, pod spike lax, and tubercles on the stem 

 green. There were three plants distinctly of the pycnocarpa type 

 with small flowers, but no red color was observed. All these 39 

 plants probably belong to the pycnocarpa type so far as the rosettes 

 are concerned, as well as edge character of the leaves. 



In all of the hybrid types it has been observed that the color is 

 very variable, especially that of the calyx buds. Also it has been 

 observed that there is a variation in size of the flowers, some of the 

 plants having small flowers, others large. I have suspected that 

 there was further splitting of the types in regard to flower size, but 

 it was impossible with the amount of other work on hand to study 

 flower size, or color behavior in either the F^ or F2 cultures. The 

 studies have been confined largely to the rosettes, exclusively so in 

 the Fo. It would be of interest, however, to study carefully flower 

 and color behavior in the F^ and Fo hybrids. 



One of the very marked difl^erences between the two hybrid types 

 is the length and general habit of the fruiting spike in the annual 

 forms, and this feature in each twin is in strong contrast to the 

 fruiting spikes of the parents. In the pycnocarpa type the density 

 of the foliage and broader leaves, or lower bracts, contrast well 

 with the open foliage and narrow leaves, or lower bracts, of the 

 lamarcklana type. The relative width of the leaves, and their 

 crinkled, or noncrinkled character, parallels these features in the 

 rosettes of the twins. The dift'erences in length of the fruiting 

 spike were very striking in this annual culture. While this feature 

 has not been carefully analyzed in biennial cultures, I doubt if 

 the variation in biennial cultures is so great. Even in annual cul- 

 tures I am inclined to believe that the results would vary to some 

 extent with the season, and the time of the year when stem develop- 

 ment began. In the reciprocal cross the same features were pre- 

 sented in the fruiting spikes of the twin hybrids. 



Cultures of ipi6: Biennial. 



In the autumn of 191 5 seed was harvested from protected plants, 

 of parents, and twin hybrids of the reciprocal crosses except the 

 pycnocarpa type of lamarckiana X pycnocarpa. The seed was 

 planted in pans during April, 1916, transplanted to 2 inch, or 2^ 



PROG. AMER. PHIL. SOC. , VOL. LVI, J, JUNE 25, I918. 



